Airfield Models - Wing Construction Example

Glue Ribs and Shear Webs in a Model Airplane Wing

May 03, 2015



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Airfield Models (http://www.airfieldmodels.com/)Gluing Ribs and Shear Webs in a Model Aircraft Wing

At this point I have spent less than 20 minutes fitting the parts and getting everything set up to ensure the wing will be straight.  This page will cover gluing the ribs and shear webs in place.

I advocate using Carpenter's glue because it has a long working time as well as being neater the excess cleans up easily.  What you should notice is that the greatest amount of time spent building this wing is preparing parts and getting them aligned properly not applying glue or waiting for it to dry.  Any carpenter's glue will work fine.

I do not use CA because it is messy, expensive and does not allow time to adjust parts.  The mess will not be so important here because it will be under sheeting.  Nevertheless, I look at every project as building experience.  The only way I know I can build a good looking structure is to always strive towards that goal.  For example, when using a transparent covering I do not want to see misaligned parts or glue all over.

 
 
Use Carpenter's Glue for general construction.  Here the center rib glued in place with the plywood webs.

The center rib is carefully aligned and glued in place along with the plywood shear webs.  I cut both webs at the same time using double-stick tape to hold the blanks together.  To ensure that they are placed in the structure the same way I marked them while they were still stacked.  You can see the marks on the upper, outside corners.

The holes are supposed to be centered top to bottom but they are probably off a bit.  Positioning these webs with the same side up will ensure the dowels are parallel.

This step took less than two minutes

Elapsed time 20 minutes

Stack the ribs together and add glue to the spar notches. It is possible to glue each rib and web individually, but that is time consuming.  I like to speed things up here and the following method works well for me.

Clamp the ribs into two stacks and do the same with the webs.  Add glue to one stack of ribs and webs all at once.  After these parts are positioned and pinned in place repeat with the second stack.  This takes less time and is less tedious than adding glue to each rib and web individually.

Do not attempt this if you are using CA. The love of CA is the root of all evil.

This step took 2 minutes (including aligning and clamping)

Elapsed time 22 minutes

Glue the ribs and shear webs to the lower spar. Starting at the center (or wing root), glue in a rib and web.  Continue with that pattern until all the ribs are in place for one panel.  Repeat for the other panel.

Ensure the webs are centered on the spar and stand perpendicular to the board.  If you slot the spars as I have done, then it is important for the webs to fit into the slots or the upper spar will not be seat properly.

If the webs are cut properly they will hold the ribs perpendicular to the board, but you still have to align them fore to aft.

All the ribs in place. All the ribs are in place and the straight edge has been placed on the ribs to hold them against the stick I put in place earlier.  The stick is not visible in this image.

This step took 6 minutes

Elapsed time 28 minutes

Glue in the upper spar. Glue is placed in the spar slot of each rib using a toothpick, popsicle stick or small spatula.  A thin bead of glue is run down the groove of the top spar.  The spar is carefully pushed in place starting at the center and working toward the tips.

The glue swells the wood slightly making the fit tighter so the spar will not slide in place as easily as it did when you dry fit the parts.

Do not try to push the spar all the way down in one shot.  Instead, work your way back and forth along the wing pushing it a little way into each rib until it is fully seated.

If you push it in all at once then the spar can push the ribs on either side of it out slightly.  In other words adjacent ribs will cant away from the rib you pushed the spar into.

In this case the fit is excellent so no clamps or pins are necessary.  Be sure the wing remains flat on the board.  A small amount of weight, such as magazines, will hold the wing down.  Weight wasn't necessary here because the wing stayed flat on the board but it wouldn't hurt to use some anyway.  This step took 4 minutes.

Elapsed time 32 minutes.

 
 

I mentioned on the previous page that once I start a wing construction I can not stop.  The reason for that is because it is important to get the webs lined up between the spars.  If you do part of the work and let the glue dry before it is complete there is a good possibility some of the webs will not line up. You will be in a situation where you have to force them in place or cut them loose.  I prefer to get it all lined up while the glue is wet and avoid any problems.

This is a potential stopping point.  However, there is one more step I want to take before stopping because the next step after that requires the glue to be thoroughly dry.  That step is gluing on the sub-leading edge and the trailing edge.

Gluing them in place only takes a few minutes.  If I wait until the next day to glue them on then I will be stuck waiting for them to dry before I can proceed.  If I get them glued in now I can let the whole assembly dry and then move quite a bit further in the construction tomorrow.

 
 

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Jigging and Dry-Fitting a Model Aircraft Wing
Adding the Sub-Leading and Trailing Edges

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Copyright 2003 Paul K. Johnson